Reaching a goal can feel rewarding, but sometimes the excitement fades quickly afterward. Why do you think that happens? Is it about the journey more than the result? Have you ever achieved something that felt less satisfying than expected?
Not like the goals becomes meaningless, it's more like you tend to feel empty once you have achieved your goal. This is why most people tend to look for more goals once they achieve one.
Human beings always strive to get more, once they have something, they look forward to something else. reaching a goal is just a step, once you step into your goal, you will see another step.